Table.1. Molecular properties of senescence barriers encountered by cultured HMEC

SENESCENCE
BARRIER

Morphology

SA-β-Gal

p16

p53

Arrest

LI(%)

Karyotype

Mean
TRF

53BP1
foci

ser15P
p53

STASIS
(stress-associated)

senescent#

+

+

IND

viable in G1

<2

normal

~6-9kb

+

-/+

Replicative Senescence:
AGONESCENCE

senescent

+

-

+

mostly viable all phases, some death

~15

abnormal

~4-5kb

+++

++

Replicative Senescence:
CRISIS

growing,
dying,
debris

+

-

-

eventual massive death

~40

abnormal

<5kb

ND

ND

OIS

sick, dying,
debris

-/?*

IND

IND

all phases

~15

IND

IND

ND

ND

Isogenic
Fibroblast
SENESCENCE

senescent

+

+

IND

viable in G1

<2

normal

~6kb

+

-

IND: senescence barrier independent of that property; ND: not determined
#: HMEC arrested at stasis in MCDB 170 have a morphology showing abundant stress fibers
*: negative in pre-stasis HMEC; could not be determined in post-selection HMEC. 
The expression of 53BP1 foci and serine 15 phosphorylated p53 are markers of a DDR.